Enormous amounts of waste heat are generated by a wide variety of industrial and commercial processes and operations. Example sources of waste heat include heat from space heating assemblies, steam boilers, engines, and cooling systems. With the use of low grade waste heat, such as waste heat having a temperature of below about 400 degrees Fahrenheit (about 204 degrees Celsius) for example, conventional heat recovery systems generally do not operate with sufficient efficiency to make the recovery of energy cost effective. The net result is that vast quantities of waste heat are simply dumped into the atmosphere, the ground, the water, or other types of surroundings without producing useful work.
The efficient integration of low temperature heat sources into a simple organic rankine cycle system to increase net power output, however, may pose thermodynamic challenges. Specifically, the low temperature heat sources generally compete against each other in terms of temperature and capacitance rate such that the overall recovery of heat may be limited.
There is thus a desire for an improved organic rankine cycle system or other type of waste heat system that effectively recovers waste heat over a wide temperature range from multiple low grade heat sources at different operating conditions. For example, the waste heat of one or more charge air coolers may be incorporated into an organic rankine cycle system that otherwise would be dissipated without producing useful work. Such a system would efficiently use the waste heat for increased net power output.